2. Spin Devices
To study the physical and chemical properties of materials based on the standard spin-dependent states (collinear) in ferromagnetic (FM) or anti-ferromagnetic (AFM) configurations, the Kohn-Sham single-particle wave functions are represented as products of spatial orbitals with up- or down-spinors. In these cases, the magnetic moment from the system is collinear with the chosen spin quantization axis. In this tutorial, using the first-principles density functional theory (DFT) with the local density approximation combined with the nonequilibrium Green’s function (NEGF) formalism as implemented in the NanoDCAL code [TGW01], you will study the spin electron transport properties through a variety of devices geometries, and different analysis tools. Moreover, electrons have two intrinsic attributes, which are charge and spin angular momentum. In particular, the arrangement and orientation of the spins into the material not only directly determine the magnetic properties, but also strongly affect other physical properties, such as the transport, optical, and thermal properties [BBF88]. The spin arrangement into the structures is generally classified as collinear spin and noncollinear spin. Materials with a noncollinear spin structure can be ferrimagnets, antiferromagnetic, and ferromagnets. Moreover, we can further classify the noncollinear spin structure into coplanar and noncoplanar structures [QYW20]. Investigating the spin properties into semiconductors using electron charge and spin as information carriers together, might offer a major advance toward creating organic devices. For instance, these devices might exploit spin-dependent effects, while incorporating standard semiconductor technologies, providing non-volatile, low-power, high-speed, and highly integrated advantage [WAB01].